It sounds like you are a rather emotionally independent woman who knows what she wants—and knows what she doesn’t want. If you are in a place in your life for whatever reason that you prefer not to date or be in a serious relationship that is totally OK. You don’t want to be in a relationship (or looking for one) right now and you don’t want to be hassled for that decision
There are lots of reasons why people want to be in a serious relationship and lots of reasons why they prefer not to be. There are good and bad reasons to be in a relationship and good and bad reasons not to be in one.
People want to be in relationships for many positive reasons: companionship, someone with whom to share life’s joys and sorrows, the greater ease of life that can come from being part of a “team”. Love, physical affection and having someone in your corner when life is hard are other good reasons for being in a relationship.
More problematic reasons are not feeling that you are OK or can be happy without another person, wanting to be completely taken care of financially or emotionally and expecting another person to “save you” from life or from your own aloneness. Mainly these are problematic because they don’t work and they don’t solve the underlying problems in yourself that leads to those needs in the first place.
There are also good and bad reasons not to be in a relationship. Dating takes a lot of energy and can be a roller-coaster of hope and disappointment. Sometimes we just don’t have the emotional reserves or we’re just not up for it. Other good reasons for not being in a relationship are having the desire to enjoy being independent and self-sufficient or even to prove to yourself that you can be. When you feel comfortable being on your own being with someone is a choice, not an act of desperation. Perhaps the best reason of all is that you don’t want to be in a relationship. If you are in a relationship and don’t want to be, how satisfying can that possibly be for you or your partner?
Not-so-good reasons for not being in a relationship include wanting to be in a relationship but feeling stopped by fear or not feeling worthy or deserving. Or if you feel stuck because it has been a few years and you are not yet over your former partner then you should address this issue and get free of that emotional suffering. Similarly, if you are avoiding dating because of social anxiety or confidence problems, these too can be addressed. Avoidance is not the solution.
Regarding the problem of being nagged by others who care about you, this is best handled directly. You can say something straightforward, such as “It makes me feel bad when you frequently ask me these questions. Please don’t do that.” Or you can use humor, as long as it is not biting or too sarcastic. You have the right to your own decisions and you may or may not wish to share your personal reasons with anyone; that is completely up to you, so It’s OK to politely tell others to butt out.